Discover Mathematics P5: Term 2, Unit 9, Lessons 9–13
GoalUnderstand that a fraction is a division of the top number by the bottom number, and share whole things equally.
New words
dividend · the number that is shared, written on top of the fractiondivisor · the number of equal shares, written at the bottom of the fractionquotient · the answer to a division, which can be a fraction or a mixed number
Explanation
When you share whole things equally, the answer can be a fraction. If 3 loaves of flatbread are shared by 4 children, each child gets 3 ÷ 4 = 3/4 of a loaf. To see why, cut every loaf into 4 equal quarters. There are 12 quarters, and each child gets 3 of them. So a fraction bar means divide: the numerator is divided by the denominator, a ÷ b = a/b. This works when a is bigger than b too. 5 ÷ 2 = 5/2 = 2 1/2: 5 metres of rope cut into 2 equal pieces gives pieces of 2 1/2 metres. To change an improper fraction into a mixed number, divide the numerator by the denominator: the quotient is the whole part and the remainder is the new numerator. Check by multiplying: 4 × 3/4 = 3.
Division
Fraction
Mixed number
3 ÷ 4
3/4
3/4
5 ÷ 2
5/2
2 1/2
7 ÷ 3
7/3
2 1/3
12 ÷ 5
12/5
2 2/5
Worked examples
Three loaves are shared equally by 4 children. 3 ÷ 4 = 3/4, so each child gets 3/4 of a loaf. Check: four shares of 3/4 make 4 × 3/4 = 12/4 = 3 loaves.
A rope 5 m long is cut into 2 equal pieces. 5 ÷ 2 = 5/2. Since 5 = 2 × 2 + 1, the mixed number is 2 1/2. Each piece is 2 1/2 m long.
A shop packs 17 kg of rice into 5 equal bags. 17 ÷ 5 = 17/5. Since 17 = 3 × 5 + 2, the answer is 3 2/5 kg in each bag. Check: 5 × 17/5 = 17.
Class activity
Share the paper. Take 5 sheets of paper and share them equally among 4 people by folding each sheet into quarters. How many quarters does each person get? Write the division 5 ÷ 4, the fraction 5/4 and the mixed number 1 1/4. Then try 3 sheets shared by 2 people.
Practice
1
Write 2 ÷ 5 as a fraction.
2/5.
2
Write 9 ÷ 4 as a fraction and as a mixed number.
9/4 = 2 1/4.
3
11 L of juice are poured equally into 3 jugs. How much is in each jug?
11 ÷ 3 = 11/3 = 3 2/3 L.
4
Mariam writes 4 ÷ 7 = 7/4. What is her mistake?
The number that is shared goes on top. 4 ÷ 7 = 4/7. (7/4 would be 7 ÷ 4.)